Is it safe to file off the "lawyer lips" - the little tabs on the end of the fork dropouts - on my carbon road fork? What about cyclocross forks? I've heard it's "common sense" to remove them...
Depends on the fork and the brake type used. With disc brakes, don't do it. A disc can generate enough force to pull a wheel. That's why most, if not all new MTB forks come with a burly, deep recess for the QR and the dropouts face forward. With the caliper on the back of the leg, it wants to drive the hub downward when the brakes are on. If the dropout is closer to horizontal, then it pushes the hub axle into the fork instead of out of the dropout. It's another reason why fork manufacturers are switching to thru axle forks. Stiffer, yes, but also less chance of a lawsuit.
On road and cross forks, you are probably okay, especially if the "lawyer lips" are tiny. A couple of little bumps missing aren't going to do much. If the fork has a recessed area for the QR molded into the dropout, then the effort needed to remove them is going to suck and you might affect the integrity of the dropout. Of course, you will void the warranty.
Something to think about. Pro teams file them off and there are no reports of riders crashing because the wheel came out. Of course, all of the equipment is top shelf stuff, maintained by some of the world's best mechanics, and gets replaced instantly if there is a hint of an issue. Also, no Pro is on any fork older than a year, if that. Most likely, the bike they race on is less than 6 months old.
With rim brakes they give a slight safety benefit, making it less likely that a slightly loose QR will let the wheel fall out. But the main cause of the front wheel falling out is people putting the wheel in and forgetting to do up the quick release. Lawyer lips don't do anything to stop that happening (since to get the wheel in you have to loosen enough...).
With disk brakes it's a completely different story. For historical reasons the caliper is on the wrong side of the fork, meaning the braking force pushes the axle out of the dropouts. It's unlikely you can do up a quick release firmly enough to stop the wheel pulling out of the dropouts in an emergency stop, so you must leave the lips in place.
I have had a bike without lawyer lips but with disk brakes. The one time I did an emergency stop the front wheel bounced across the road and I hit it. Not fun at all, but fortunately(?) easily reproducible. Repeatedly, until the quick release skewer broke from over-tightening.
No it is not safe as it removes a fail safe from the bike.
The UCI has banned the practice in 2013 under the bike modification rule. It is understood this was done to bring UCI rules in line with French Law to remove an unfair disadvantage faced by French teams. The UCI will be putting "UCI approved" stickers on more than just frames this year and will include forks.
The lawyer lips worked as a fail safe but their removal only saved seconds from a wheel change. Only relevant if the peloton was racing away!