In the US the law makes it illegal to 'circumvent a technological measure', defined as:

> descramble a scrambled work, to decrypt an encrypted work, or otherwise to avoid, bypass, remove, deactivate, or impair a technological measure, without the authority of the copyright owner

where

> a technological measure “effectively controls access to a work” if the measure, in the ordinary course of its operation, requires the application of information, or a process or a treatment, with the authority of the copyright owner, to gain access to the work.

A sticker doesn't count as a "technological measure".

A sticker on the data side of the disc, then! Removing the sticker is a process.