Thats why you need to find out the rules before you start detecting. A few countries don't worry about finds unless they are pre 1600. Many set the line at 1700. Others say no detecting for antiquities but you can search for modern losses, I think its fifty or sixty years old in Italy. If you find something older its your good luck but the difficulty comes when lots of older items turn up. If you found a Roman site there could be a few hundred coins/artifacts surrounding it. You should at this point stop (which is very hard to do) and report to the local authorities.
In the U.K. if you dig down to a large signal and find its a pot briming with coins then they don't want you to continue in case of damage to the hoard container. You should be credited with the finding of all those coins even though you haven't actually recovered them.
If you comply with the law you rarely lose out because even if they are not operating a Treasure Trove system there are discretionary payments that will be made to encourage people to declare their finds. Don't comply and a million dollar find would just be confiscated.
In the U.K. if you dig down to a large signal and find its a pot briming with coins then they don't want you to continue in case of damage to the hoard container. You should be credited with the finding of all those coins even though you haven't actually recovered them.
If you comply with the law you rarely lose out because even if they are not operating a Treasure Trove system there are discretionary payments that will be made to encourage people to declare their finds. Don't comply and a million dollar find would just be confiscated.