A Taiwanese local official has been sentenced to two and a half years for taking a free China-paid trip, a warning shot for grassroots politicians ahead of elections.

• A borough chief in New Taipei's Tucheng district organized a group tour to China where the hosts covered costs on the ground, and his conviction under the anti-infiltration law is now final.
• Similar cases against other borough chiefs have split — some guilty, some acquitted — because everything turns on the details.
• The line is whether the freebie counts as payment for something: heavily discounted or free meals, hotels, tickets and gifts raise red flags.
• The second test is intent — if Chinese officials push people to back a particular side or candidate during the trip, the hospitality becomes a bribe.
• Group leaders who knew about the election angle and went ahead anyway are the most likely to be convicted.

Outlook: Prosecutors are sending letters to borough chiefs across Taiwan warning against vote-buying and foreign election meddling, so expect more cases as the next election nears.