Earlier this month, six human rights watchdogs, media organisations and bloggers successfully applied for a temporary court injunction against the rules.
But the government overturned that injection at an appeal hearing on Tuesday in a case that activists have condemned as an attack on free speech.
“Following this ruling … owners of social media platforms that are used to disseminate news such as blogs, online TV and radio are required to continue with the registration process and observe ethics outlined in the relevant regulations,” government spokesman Hassan Abbasi said in a statement.
The new rules require bloggers to pay a registration and licence fee of up to $900 (680 pounds) and disclose details of shareholders, share capital, citizenship of owners, staff qualification and training programmes, as well as a tax clearance certificate to obtain an operating licence from the regulator.
Bloggers convicted of defying the new rules could be fined at least 5 million shillings (£1,661) or face imprisonment for a minimum 12 months, or both.
Digital activists say the rules are the latest crackdown on dissent and free speech by President John Magufuli, who was elected in 2015 on pledges to speed up economic growth and rein in corruption.
Several Tanzanian bloggers have already begun shutting down their websites to avoid punitive action under the new regulations.
The number of internet users in Tanzania rose 16 percent in 2017 to 23 million – around 44 percent of the population – with most using their smartphones to go online.
Last month, Uganda, another East African country acting to regulate internet use, announced plans to slap a new tax on social media users.