Recently, I was involved in a discussion of legal opinions regarding issues of significant legal uncertainty.  The 2005 Report of the erstwhile Corporations Committee of the equally erstwhile Business Law Section of the still existing State Bar of California addresses this issue as follows:

"There are several customary formats for reasoned opinions.  Historically, 'would hold' opinions (expressing a view as to what a court 'would hold') were generally regarded as expressing the strongest degree of conviction, and 'should hold' opinions were expressing a somewhat lesser degree of conviction and as a more appropriate for areas involving a relatively high degree of legal uncertainty or involving significant policy issues.  Recent reports take the position, however, that there is no difference in meaning between a 'would hold' and a 'should hold' opinion." (footnote omitted)

Is there really no difference in meaning between "would" and "should"?  I think that the question arises from the four hundred year old confusion over "will" and "shall"  See When Shall/Will/Must/May We Meet Again?  The reason is that "would" is the past tense of "will" and "should" is the past tense of "shall".  If people aren't sure about the present tense of "will" and "shall", why should they be any more certain about the past tenses of these words? 

Although "would" and "should" are auxiliary verbs in the past tense, English speakers do not necessarily use them to express past action.  For example, someone might ask "How would the court decide?" which is the same as asking "How will the court decide?".  Therefore, what John Wallis wrote nearly four centuries ago in Grammatica Linguae Anglicae remains true today:

"Quoniam autem extraneis satis est cognitu diffficile, quando hoc vel illud dicendum est (non enim promiscue dicimus shall et will)  (Since it is hard enough for strangers to know, when this or that must be said (for we say 'shall' and 'will' indiscriminately) . . .".