Clause 6 of the Tongan constitution of 1875 declares the Sabbath day sacred in Tonga for ever, forbids the transaction of trade or the playing of games or work on that day, and provides that any agreement made or witnessed on the Sabbath is void and of no legal effect. It is not a preamble sentiment; it is an operative provision that voids contracts.
The practical result is one of the most complete weekly shutdowns anywhere. Shops close, markets close, public transport largely stops, commercial fishing and most work cease, and airlines have historically arranged schedules around it. Church attendance, in a country with several large denominations, fills the morning, and the day is otherwise given to family meals and rest.
Exceptions exist for necessity: hospitals, emergency services, essential utilities and the feeding of livestock. Tourist resorts on outer islands operate under separate arrangements, which has been a periodic subject of complaint.
The provision has been tested. A commercial dispute over whether an agreement made on a Sunday could be enforced turns directly on Clause 6, and the courts have had to consider how far the voiding provision reaches. Proposals to relax the rule for particular industries, including for flights and for fishing, have been raised repeatedly and have generally failed against strong church and public opposition.
Two observations. First, the clause is one of the very few examples in a modern constitution of a specifically sabbatarian rule with contractual consequences, which makes Tonga a standing case study in comparative constitutional law. Second, it is popular. The pressure to change it has come mostly from outside, and the pressure to keep it from inside.