Antitrust regulators are feeling their oats, after years of being viewed as little more than speedbumps on the path toward corporate consolidation.

Driving the news: Insurance brokers Aon (NYSE: AON) and Willis Towers Watson (Nasdaq: WLTW) this morning terminated their $34 billion merger agreement, just five weeks after the U.S. Department of Justice sued to block the deal.

• This had been the Biden administration's first major antitrust action, with the DOJ's complaint citing an unidentified Aon executive who crowed about how the merger would create an "oligopoly."
• Aon will pay a $1 billion termination fee to Willis Towers Watson. No word yet on if it will now keep its U.S. retirement business, which it had planned to sell to Aquiline Capital Partners in an effort to help obtain DOJ approval for WTW (Aon didn't return email on that, and Aquiline declined comment).
• And none of this has to do with Big Tech, which is expected to have critics running both the FTC (Lina Khan) and the DOJ's antitrust division (Jonathan Kanter, who still needs Senate approval).

Emboldened trustbusters aren't just a U.S. thing, even though Aon/WTW did receive European Commission approval. In just the past few days:

• Brazil's top competition regulatorused the word "complex" when describing Oi SA's proposed $3.2 billion sale of its mobile network operations. That is not an adjective that either the seller or the buying group wanted to hear.
• European antitrust regulatorsreportedly are launching a full investigation into Facebook's proposed $1 billion purchase of enterprise customer service company Kustomer, which was first announced last November.
• Westpac Banking Corp. of Australia was blocked by antitrust regulators in Papua New Guinea from selling a A$420 million stake in its Pacific operations to Kina Securities. That deal was announced last December.
• An Indian courtdenied Amazon and Flipkart's appeals to slow down an antitrust investigation into their business practices.

The bottom line: The path from deal announcement to deal closure is no longer perfunctory.