"firmly interpreted" is a correct and usable phrase in written English.
It means that something was interpreted in a strong and unwavering manner. One example of using this phrase in a sentence could be: "The Constitution should be firmly interpreted to protect the rights of all citizens, regardless of their race or gender."
Concerned about a repetition of French adventurism in Mexico, Hayes interpreted the Monroe Doctrine firmly.
The visit could thus be interpreted as a warning from Iran that it stands firmly behind Hezbollah, and that anyone who is thinking of taking action against Hezbollah, be it political or military, should think twice.
This type of stage allowed for fluid movement and considerable intimacy between actors and audience, while its lack of scenery placed the emphasis firmly on the actor interpreting the playwright's words.
Saying that he would "firmly protect the patriotic enthusiasm of the young people of China" – which the students interpreted as a message of support – Wan cut his Canadian visit short and headed home.
In a response interpreted later as a "shot across the bows" aimed at Hammond, Wall told Arbuthnot, firmly: "Yes, and I'm sure that's not intended".
Some interpreted it to mean that every email deserved a reply, which only shackled them more firmly to their inboxes.
But the consciousness of this novel is also firmly grounded in the west, in America, in the rootlessness passed down through generations of immigrants and interpreted in myriad subjectivities.
This precluded us from assessing the long-term health sequelae of smoking, and it also meant that the associations documented cannot be interpreted as causal, since the appropriate temporal relation between smoking status and health indicators cannot be firmly established.
These ranges are difficult to interpret, as no firmly established willingness-to-pay benchmarks exist for venous thromboembolism prevention.
