Musk thistle (Carduus nutans L.), Scotch thistle (Onopordum acanthium L.), and Canada thistle (Cirsium arvense) are designated as noxious weeds and must be controlled by the landowner. Bull thistle (Cirsium vulgare) rarely reaches infestation levels and is not considered a noxious weed but should probably be controlled when possible. For more information on the laws contact the Oklahoma Department of Agriculture, Food, and Forestry, https://ag.ok.gov/. Here is a link to the Oklahoma Noxious Weed Law and Rules - https://ag.ok.gov/wp-content/uploads/2020/11/Oklahoma-Noxious-Weed-Law.pdf. In addition, here is a fact sheet that discusses control of these weeds - https://extension.okstate.edu/fact-sheets/integrated-management-of-invasive-thistles-in-oklahoma.html.