I am in the USCGR as well as a full time police officer. Any employer (including LE agencies) are required by federal law to give members of the reserves time away from work. My state also requires that I be given 15 days of PAID leave per year. The federal law also states that you continue to build seniority, ect., as if you were still there.
While that applies to someone already working, the same law prohibits employers from discriminating against a potential employee based on military status. Does it happen? Probably. Just make sure you are completely honest with your prospective employer about your military status. While they cannot decide not to hire you based on the military, they can probably fire you for lying during the hiring process.