To expand on my comment: I looked at a source which claims to contain information on EU law in concise way (explanation of EU law for newsletters). Here is what you must do if you want to send a newsletter to EU citizens:
- You have to get them to agree to getting the newsletter. If they gave you their e-mail for another purpose, e.g. password recovery, it is illegal to send a newsletter to this address. You need their explicit consent.
- To get their explicit consent, you have to offer them an opt-in. Opt-out is not sufficient to comply with the law. So, if you have a "send me a newsletter" option on the registration screen, it has to be unchecked by default.
- The user has to be able to opt out anytime. Each newsletter issue must point that out anew.
These laws arise from EU Directive 2002/58/EC Directive 2002/58/EC, Directive 2003/58/EC and Amending Council Directive 68/151/EEC. These being EU directives, it means that in each individual EU country, there should be a country specific law implementing each the directive. The country specific laws can be just as the directive, or more strict, but not more permissive.
The law as stated above does not say explicitely that you cannot refuse your services to somebody who refuses to sign up for your newsletter. I strongly suspect that, if you choose to do so, the customer has to be informed about the restriction before he pays for using your app, and you probably have to return his money if he cannot use the application because he exercises his right to refuse the newsletter bundled with the app.
I may have gotten some of the details wrong, and even if they are right, maybe there is some legal loophole which will allow you to implement the compulsory newsletter application. But I think you can see that the law is written with strong customer protection in mind, so if you get sued, the spirit of the law will be against you. And the sentiment of your own customers as well. My advice is to refuse to implement this before your employer has had a consultation with a lawyer aware of EU laws.