This is not correct. Companies conducting buybacks do so at a low rate over a long period of time exactly to avoid having the impact that you're describing. Companies buy their shares back at the market price, and the normal transaction volume of a large companies shares dwarf the size of buybacks it may be conducting.
Why would there be a specific law covering this situation? It's an obvious violation of fiduciary responsibility to buy back shares in an inefficient, price-elevating fashion.
