Depends, it can come down to your corporate employment contracts and corporate policies. Also, if you work for a public company, you usually have a fiduciary duty to shareholders at a certain managerial level, so it falls into the illegal territory.
If you own your own company, it's usually not a big deal to let people wine and dine you lol
It is illegal if you're a government employee or working as a government contractor. What most people get in trouble for is laundering the money that they're taking in bribes.
If you own your own company, it's usually not a big deal to let people wine and dine you lol