Individuals who remove signs can face criminal mischief or theft charges.
Once installed on your neighbor's front yard, a political sign is considered their property. The level of criminal charge, and thus the penalty, depends on the value of the sign.
For a small sign worth less than $100, a theft or criminal mischief charge would be a Class C misdemeanor, with a maximum penalty of a $500 fine.
If the sign is larger and worth more, or the facts of the case warrant a criminal trespassing charge, the offense could be Class B misdemeanor and punishable by up to 180 days in jail and a maximum $2,000 fine.
Political signs are not permitted on public property, but their removal is the responsibility of the governmental owner. For example, crews with the Texas Department of Transportation can remove political signs installed in the right of way along highways and farm-to-market roads.