Transferring money to spouse for investing in stocks

Hello,

1) If a person transfers money to spouse's account for investing in stocks, how will taxes on returns be treated if they fall in different tax brackets?

To be specific, capital gains is taxed at flat rates (15%/10% for STCG/LTCG) and not dependent on individual tax bracket. So if a person in 30% bracket transfers money to spouse who is in 20% bracket, and the spouse invests this money in stocks, at what rates will the returns be taxed? 30% or 20% or at flat rates (STCG/LTCG)?

2) Is it legal to do so?

Thanks in advance.