How to obtain alienation from the rights to the program code?

Question

Intellectual property

Good afternoon.
The situation is this: I ordered a certain service from the developers.
The development is coming to an end and due to some circumstances, I transfer the further development and development of the service to other programmers.
Let's say 3 years pass, my service will become in demand and will bring good money, will my first developers be able to somehow "declare" the right to own this service?
For development, I did not conclude any contracts with them, all that is - only electronic correspondence.
Do I need to somehow get them to refuse ownership of the program code?
How does this happen and what are the consequences if they, for example, do not want to sign such an agreement?
PS: the developers are outsourced, they are located in another country.

Answer 1

Every relationship must have a contract. Here in the contract and paint to whom the money, and to whom the right to intellectual property.

Answer 2

don't be arrogant
, firstly, the code will not be recognized
in three years; secondly, you are not in the USA