NEW DELHI (AP) — The U.N. says government bans on plastic can be effective in cutting back on waste but poor planning and follow-through have left many such bans ineffective.

The report, released Tuesday on U.N. World Environment Day, notes that rules limiting the use of plastic bags had decreased their use in places like Morocco, Rwanda and parts of China, sometimes significantly. But elsewhere things haven't gone so well.

A ban on disposable plastics in New Delhi, for instance, has had only limited impact. The city has tried repeatedly over the past decade to ban the use of thin plastic bags, but they remain ubiquitous. Elsewhere in India, including the states of Sikkim and Himachal Pradesh, there have been better results.