Note I said be careful, not don’t do it. Here is an example of Wa and Oregon rules
PETRIFIED WOOD: Petrified wood is available for collection on a free use basis in limited quantities as long as the collection is for personal, non-commercial purposes. According to Federal regulations (43 CFR 3622), free use collection weights are limited to 25 pounds plus one piece per day, not to exceed 250 pounds in one calendar year, and no specimen greater than 250 pounds may be collected without a special permit. The petrified wood must be for personal use only, and shall not be sold or bartered to commercial dealers. A material sale contract must be obtained from a BLM Field Office for collection of more than 250 pounds a year, or for commercial use. Mining claims may not be staked for petrified wood.