Careful with USEERA/ESGR. It works well for airlines and many blue collar jobs because they use seniority systems which make it VERY hard for the company to jerk you around on a whim, because most of the punitive actions would violate seniority which is protected in a black-and-white manner. Also job performance evaluation is much more objective and transparent than in white collar (did you pass sim this year? Good-to-go. Did you install X number of bolts on the assembly line? Good-to-go.) If they want to say deny a promotion from FO to CA, they would need concrete justification, AND the ability to show that this was consistent with past practices for other employees.
White-collar salaried employees OTOH are largely at the mercy of the employer. If you push back too hard, involve the unit/ESGR, they typically fall into line for a while but payback will be a you-know-what down the line. BTDT, and seen it countless times with my reserve personnel. It's very predictable and consistent, almost like clockwork, 18-24 months out. Then they'll start documenting your inevitable performance failings, and building the paper trail. They often won't actually fire you, but the toxic climate will encourage most folks to leave on their own. And you'll be at the very pinnacle of the layoff list, in the event legitimate layoffs occur they'll sweep you away under that cover. Not a nice way to live life.
My recommendations for dealing with white collar employers...
1) Try to educate them. In some cases, USEERA violations are due to lack of knowledge, or misunderstanding. Common if they have few or no other reservists, management and HR may have simply not experienced the various issues. Common assumption is that mil duty is "only" one weekend a month and two weeks a year...and they'll often "assume" you'll take vacation for the two weeks. If you're fairly senior and have credibility, you can have this conversation with them yourself (review applicable rules and bring documentation to back up your explanation). If you're junior, you may want to bring someone from the unit or even ESGR who can lend credibility and articulate your position...but let them know in advance, and let them know the person is there to educate so they don't think you're lawyering up.
2) If it's clear they know better (or don't care) and are intentionally punishing you, it's probably because they are resentful and feel you're taking advantage or leaving them in a bad spot. In this case there's bad blood you have to overcome. Best approach here is to request a meeting and portray yourself as being caught in a bind between mil and civilian job, ie your military obligation is making it hard to devote the necessary time to your civilian job. You just want to fulfill your current obligation/tour or get to 20. Basically make it you and the boss against the military. If you can convince the employer that they're really your priority, and you're just stuck with military for the time being you may be able to buy some sympathy and time. You'll probably want to make some visible concessions such as perhaps fewer weekday drills for a while. Unless you really are near the end of your mil career, you may want to use the breathing room to look for a better job.
3) If it's just going nowhere fast, better find a new job. Maybe your network can help you find employers which are more tolerant of reserves.
Is this the spirit and intent of USEERA? Absolutely not. But unfortunately it's the reality in many cases, and one of the reasons I gave up white collar to do airlines. And I don't entirely blame the employers...if key employees who are mil (often leaders/managers) leave at awkward times it can really put the organization in bind. Reserve duty (as it exists in the post 9/11 world) is not particularly compatible with all civilian jobs.
You can fight it to the hilt, but that's likely to be ugly and toxic and they'll get you in the end if that's what they want to do. Managers have long memories and hold grudges. And then you'll have baggage in the form of a disciplinary track record. And of course you don't want to tell a potential future employer that you got unfairly disciplined for taking too much mil leave...