We've found, through 30 years of not only running one of the best casual tennis leagues in the country, that what you address in your league's constitution and guidelines, sets forth in motion, a foundation for many hours and years of fun and competitive tennis, unless the people (not simply players) in your group just simply suck at being people.
You may wish to use the following to establish your guidelines regarding absenteeism:
Absenteeism is neither a crime nor a penalty as much as it is a self-inflicted wound. You will truly hate yourself and feel ill if you miss a "Your League or Group" play day or event.
For the new "Your League or Group" member, the act, much less the thought of missing a play day, is strongly over-ridden and negated by the novelty and excitement which has been experienced by our new league players for generations [We can back this, but you may want to check with your attorney].
As much as absenteeism is not mentioned (written) in our league guidelines, rules and constitution, it is still felt as an act near or similar to treason or cutting a class in college for which you would ace the final if called upon to do so.
Over time however; even the most seasoned "Your League or Group" player will find that life, work, school, medical emergencies, weddings, funerals, yard work, silly holidays, road construction, laundry, un-called-for dental appointments, deer season, happy hour, anniversaries, birthdays, road-trips, graduations, baby showers and other such nonsensical tasks and events will interfere with their obligated time on-court.
For this we have established the following Acceptable Excuses for being absent from a "Your League or Group" event:
Weddings - Unless you don't know either the bride or groom and attended simply for free food, music and beverages.
Weddings - If it's your wedding, because we are going to see you out here on the courts single in a few years and you are going to put us through all the drama in the interim.
Medical Emergencies - Only if the subject is bleeding and the trauma is life-threatening.
Yard Work - Only if you are doing so to host a party for other members.
NOTE: If you simply have a good bunch of peeps, all speaking the same language, it will work and be a whole lotta fun.