The question should be, what tax laws did he break? I used a tax law to my benefit when I lost an incredible amount of money in the Nasdaq bubble. While in the bubble I was making more each month than I made for my annual salary teaching. I was taking in $75,000 a month profit.
But, as my broker explained after the bubble burst, there's the "bull, bear and pig." I was the pig in a bull market and paid dearly when the bubble burst. An accountant was recommended for me and I saw that I could deduct a large amount of my losses that year and subsequently, a smaller amount every year after. Probably for the rest of my life, lol. But my taxes are lower due to that credit.
Did I do anything illegal? No. I used the tax laws to my advantage. Just as you would do.
And, as for making poor decisions, I stayed in those stocks because I believed in America. I just couldn't believe that they would drop to the bottom and not recover. But patriotism wasn't enough. I was committed to long term investments which usually turn out to be profitable. Alas, I, and millions of others, perhaps Trump, got caught in a bad place. Trump is smart enough to continue making billions of dollars...I just was't meant to be rich! C'est Le Vie, lol.