Hello Refrigeration Engineerers

I would really appreciate some advice please on some refrigeration pipework that I have come across.
We attended a clients site today to repair a suspected refrigerant leak. The unit is a Lennox DX system running on R407c installed approximately 10 years ago. We have found that all the copper refrigerant pipework (5/8 & 1 3/8) is seamed not seamless (as I would expect) and that all the joints are soft soldered.
I am assuming that all this pipe work is not refrigerant specification? The pipe work quality is fantastic but we are a little reluctant to strength test to 31b.
I have been looking for legislation to pass onto our clients to show that seamed copper and soft solder are not the way forward but have not come up with the conclusive proof necessary.
In your opinion should I tell him that unfortunately it is necessary to condemn all of his pipe work ( what legislation justifies this) or as it has been satisfactory for the last 10 years am I being overly cautious?