bamacrazy 

Do local races limit tire size for beginners?

flargle

Nope.

The standard verbiage on race fliers usually says "No bar-ends", meaning that everything else goes. The bar-end rule is because they are forward-facing and therefore potentially hazardous. (Nevermind that they're allowed in mass-start mtb races....)

When in doubt contact the organizer but there's no USA Cycling rule on tire width or handlebars.

saturnhr

Might be not so easy, since there is a new rule (UCI) which says 33mm maximun.
I know that some races are held outside the USACycling/UCI umbrella, but most aren't.
I agree, that they most likely let you start with whatever equipment you have, and enjoy! and have fun!
The following is hypothetical: Sometimes certain categories are poorly filled and assume there are only 2 riders in your category and you are one of them. The other gets a flat and falls behind. You win, you hardly can believe it! However, all of a sudden an official approaches you, looks at your bike and says, I am sorry you are dq-ed, somebody filed a protest against you. It might become particularly painful, that it wasn't even the other rider but his coach, mechanic or spouse (or parent) who filed the protest. You might wish at that moment - you had used other tires?

flargle

USA Cycling and the UCI are two different organizations with two different rulebooks. The UCI is the one that has historically had the restrictions on tire size, disc brakes, and "traditional bend" handlebars, not USA Cycling. This year, the UCI has allowed disc brakes, but reduced allowable tire size from 35mm to 33mm. [IOW allowing discs but making them even more of an overkill for cross than before.]

It is only races that award UCI or World Cup points that need to follow UCI regulations. In rare (rare) cases, an overzealous local race organizer may choose to enforce some UCI regulations for the highest categories, but the risk of that happening is way overblown. (I've done a race where the flyer read "Cyclocross bikes only for 'A' race" but I certainly didn't see anyone walking around measuring tires.)

For Joe Cat-3, run what you brung. If you're really nervous about it, contact the race organizer directly.

flargle

In my experience, such behavior is simply not part of the cyclocross culture. Certainly, as one progresses through the sport into higher categories, you'll want a bling race bike with all the UCI-approved gear and such, but I think it's counterproductive to expect the worst from people. If someone pulled a dooshy move like that in a typical cat 4 race, it would really be frowned upon.

Fat Boy

Ya, I don't think I've ever seen an official check anything on a bike. I've been thinking of running one of those seat tube electric motors!