Fǎnlǒngduàn fǎlǜ bǎohù le shìchǎng de gōngpíng jìngzhēng.
Antitrust laws protect fair competition in the market.
Tips
memory
反 = against, 垄断 = monopoly (literally "ridge-cut", from 孟子: a greedy trader who climbed a raised ridge to spot and corner all the buyers). So 反垄断 = "against-ridge-cutting" = antitrust.