Over the holidays, our employer decided we would be closed the Friday following Christmas Day and the Friday following New Years Day. Employees were told that if they wanted to be paid for those Fridays, they would need to put in a vacation request with HR. (Normally the policy is that we must request vacation at least two weeks in advance).
I did not submit a vacation request because I need my accrual for a planned vacation later this year.
I am an exempt salaried manager at this company for the past 3 years.
Though I was correctly paid my full salary for the pay peiod which included the Friday following Christmas (no vacation pay used), I was paid one day of my vacation accrual on the most recent check covering the Friday following New Years Day. I didn't request the vacation but they used it anyway to cover a day that I was forced to take off because my employer decided to close the office. Is this legal?

Yes it is legal. This particular question gets asked several times a week.
- The rules for Exempt Salaried employees are part of the 29 CFR 541.xxx. The docking rules are 29 CFR 541.602. However vacation/PTO is not mentioned anywhere in the federal law (FLSA) or regulations. Federal DOL is on record as saying that nothing that occurs to the vacation/PTO balance has anything to do with them as long as the salary is correctly paid according to the 541.602 rules.
- CA is interesting that for several weeks (May 30th 2001, through June 22nd 2001) CA-DLSE actually had an opinion letter supporting your position. However they formally withdrew the opinion letter and CA no longer supports this position.

Seems odd that vacation can be used that way since the law states that vacation accrual is the same as wages earned. If your employer can make unauthorized withdrawls from your accrual... particularly for a day that you were ready and willing to work... but was not permitted to, then vacation isn't wages... it's worthless.
I would view a deduction from my vacation accrual (my "wages earned") as inappropriate as defined by the docking rules you mention in your post.

Your privilege of course. I am not sure that you care, but I can give you a pointer to one of many opinions issued by federal DOL disagreeing with you.

http://www.dol.gov/esa/whd/opinion/FLSA/2005/2005_01_07_7_FLSA_PaidTimeOff.pdf