|Chelgren announced his proposal in a January 22 speech on the Senate floor. You can listen to part of his speech around the 11:00 minute mark of the January 25 On Iowa Politics podcast. Here's my transcript:
Chelgren: Currently, in the constitution of the state of Iowa, we have a defined militia, which is all able-bodied males from the ages of 18 to 45 years old. That would as of yesterday exempt me from being in the Iowa militia. I think that's unfortunate, because I feel I am still able-bodied, and if I can serve my state or serve my country, I'd be happy to do so.
Beyond that, of the fact that we are limiting the age of [service to] 45, we are also saying that males exclusively [can serve]. I would like to amend the constitution so that women may also serve this state and this great country in the militia.
What's all this about a state militia? I didn't know anything about that part of the Iowa Constitution. Here's Section 1 of Article VI:
The militia of this State shall be composed of all able-bodied [white]* male citizens, between the ages of eighteen and forty five years, except such as are or may hereafter be exempted by the laws of the United States, or of this State, and shall be armed, equipped, and trained, as the General Assembly may provide by law.
*The above section was amended in 1868 by striking the word white therefrom: See Amendment 
At the time Iowa became a state in the middle of the 19th century, neither the federal government nor the states maintained large standing armies. Governors called up militias according to needs of the time. Iowa's territorial militia was first called up in 1838 and almost got involved in a shooting war with Missouri's militia over an 1839 border dispute known as the Honey War. Iowa's territorial militia also provided 12 companies of men to fight in the Mexican-American War of 1846, shortly before statehood.
The full text of Chelgren's proposed constitutional amendment (Senate Joint Resolution 1) is here. It would rewrite Section 1 of Article VI to read, "The militia of this state shall be composed of all able-bodied citizens eighteen years of age and older, except such as are or may hereafter be exempted by the laws of the United States, or of this state; and shall be armed, equipped, and trained, as the general assembly may provide by law."
Most of the Senate Republicans are co-sponsoring this effort: Nancy Boettger, Jerry Behn, Joni Ernst, Michael Breitbach, Jake Chapman, Dan Zumbach, Rick Bertrand, Mark Segebart, Brad Zaun, Amy Sinclair, Hubert Houser, David Johnson, Ken Rozenboom, Kent Sorenson, Tim Kapucian, Bill Anderson, Dennis Guth, Sandy Greiner, Jack Whitver.
They should have done more homework. According to the official history of the Iowa National Guard,
After 1865, Iowa's Civil War regiments were disbanded. The Iowa State Militia became, once again, a collection of volunteer organizations. In 1876, these companies were organized into regiments. In 1877, the Iowa Militia was designated as the Iowa National Guard. [...]
The period from 1901 to 1916 saw a remarkable transformation of the National Guard, both nationally and in Iowa. Improvements in facilities, training and evaluation produced a well-trained, well-equipped military force, which could be confidently called to support the Regular Army in any future emergency. [...]
After World War I, the National Guard was again reorganized. By the mid-1920s, the total strength of the Iowa National Guard was more than 6,000 soldiers. By the end of the 1930s, with World War II looming on the horizon, the Iowa National Guard consisted of the 34th Infantry Division (which also included soldiers from Minnesota, North Dakota and South Dakota), the 113th Cavalry Regiment and the 124th Observation Squadron.
In effect, the Iowa state militia was supplanted by the National Guard, with the Air National Guard added later. Mike Wiser reported during the same On Iowa Politics podcast that there still is an Iowa state guard separate from the National Guard. In theory, the governor appoints officers to the state guard. Governor Terry Branstad's communications director Tim Albrecht told Wiser no one has been appointed as an officer in that body in a long time, nor has any money been appropriated toward that purpose in decades.
Col. Greg Hapgood, public affairs officer for the Iowa National Guard, spoke to me by telephone today. He confirmed that legally, the National Guard handles the functions that state militias dealt with during the 19th century (defense, responding to emergencies). Hapgood said the U.S. Department of Defense sets eligibility rules for the National Guard or the Air National Guard.
It's nice that Chelgren wants to clear a path for women to serve in the Iowa militia, but obsolete language in state constitutions no longer affects any woman's ability to serve. Women have been able to enlist in the National Guard for decades.
Col. Hapgood also confirmed that states no longer set rules regarding the maximum age to enlist in the National Guard. That too is determined at the federal level. The maximum age has changed many times, depending on the country's needs in light of foreign deployments.
I appreciate Chelgren's willingness to serve this state. No doubt he is able-bodied. He is an avid bicyclist and was a regular on RAGBRAI for years, playing the character of "Chickenman."
The bad news is that he missed his chance to serve. The maximum age to enlist in the National Guard is now 35, and the maximum age to enlist in the Air National Guard is now 40. Some allowances are made for people with prior military service; their years of active service can be subtracted from their actual age to bring them below the age limit. But Chelgren never served in any branch of the military. UPDATE and clarification: Even a person with prior service must be able to serve 20 years in the Guard by age 60 in order to enlist, which rules out people over age 45.
The bottom line is that with or without an amendment to the state constitution, women can continue to serve in the National Guard, and no Iowan over age 45 will be enlisting in any "militia" connected to the government. Pretending to stand up for the rights of women and patriotic baby boomers may become a nice talking point in Chelgren's 2014 re-election campaign, though.
Any relevant comments are welcome in this thread.
P.S.: Both parties are likely to target Senate district 41 in 2014. Chelgren surprised most Iowa politics watchers by winning his seat, containing the Democratic-leaning Ottumwa area, by fewer than a dozen votes in 2010.